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atan2: store sign bits and greater of |x| and |y|

This commit is contained in:
Matt Huszagh 2020-12-17 09:47:39 -08:00
parent cb38c3e3bd
commit 1f28949bc5
1 changed files with 16 additions and 9 deletions
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25
dsp/src/trig.rs
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@ -1,4 +1,4 @@
use super::{abs, shift_round, Complex};
use super::{shift_round, Complex};
use core::f64::consts::PI;
include!(concat!(env!("OUT_DIR"), "/cossin_table.rs"));
@ -22,11 +22,18 @@ include!(concat!(env!("OUT_DIR"), "/cossin_table.rs"));
/// corresponds to an angle of -pi and i32::MAX corresponds to an
/// angle of +pi.
pub fn atan2(y: i32, x: i32) -> i32 {
let y = y >> 16;
let x = x >> 16;
let mut y = y >> 16;
let mut x = x >> 16;
let ux = abs(x);
let uy = abs(y);
let sign = ((y >> 14) & 2) | ((x >> 15) & 1);
if sign & 1 == 1 {
x *= -1;
}
if sign & 2 == 2 {
y *= -1;
}
let y_greater = y > x;
// Uses the general procedure described in the following
// Mathematics stack exchange answer:
@ -41,7 +48,7 @@ pub fn atan2(y: i32, x: i32) -> i32 {
//
// which is taken from Rajan 2006: Efficient Approximations for
// the Arctangent Function.
let (min, max) = if ux < uy { (ux, uy) } else { (uy, ux) };
let (min, max) = if y_greater { (x, y) } else { (y, x) };
if max == 0 {
return 0;
@ -64,15 +71,15 @@ pub fn atan2(y: i32, x: i32) -> i32 {
ratio * K1 - K2 * shift_round(ratio * ratio, ATAN_ARGUMENT_BITS)
};
if uy > ux {
if y_greater {
angle = (i32::MAX >> 1) - angle;
}
if x < 0 {
if sign & 1 == 1 {
angle = i32::MAX - angle;
}
if y < 0 {
if sign & 2 == 2 {
angle *= -1;
}